Few people understand the real significance of Climategate, the now-famous hacking of emails from the University of East Anglia Climatic Research Unit (CRU). Most see the contents as demonstrating some arbitrary manipulating of various climate data sources in order to fit preconceived hypotheses (true), or as stonewalling and requesting colleagues to destroy emails to the United Nations Intergovernmental Panel on Climate Change (IPCC) in the face of potential or actual Freedom of Information requests (also true).

But there's something much, much worse going on—a silencing of climate scientists, akin to filtering what goes in the bible, that will have consequences for public policy, including the Environmental Protection Agency's (EPA) recent categorization of carbon dioxide as a "pollutant."

The bible I'm referring to, of course, is the refereed scientific literature. It's our canon, and it's all we have really had to go on in climate science (until the Internet has so rudely interrupted). When scientists make putative compendia of that literature, such as is done by the U.N. climate change panel every six years, the writers assume that the peer-reviewed literature is a true and unbiased sample of the state of climate science.

That can no longer be the case. The alliance of scientists at East Anglia, Penn State and the University Corporation for Atmospheric Research (in Boulder, Colo.) has done its best to bias it.

A refereed journal, Climate Research, published two particular papers that offended Michael Mann of Penn State and Tom Wigley of the University Corporation for Atmospheric Research. One of the papers, published in 2003 by Willie Soon and Sallie Baliunas (of the Harvard-Smithsonian Center for Astrophysics), was a meta-analysis of dozens of "paleoclimate" studies that extended back 1,000 years. They concluded that 20th-century temperatures could not confidently be considered to be warmer than those indicated at the beginning of the last millennium.

In fact, that period, known as the "Medieval Warm Period" (MWP), was generally considered warmer than the 20th century in climate textbooks and climate compendia, including those in the 1990s from the IPCC.

Then, in 1999, Mr. Mann published his famous "hockey stick" article in Geophysical Research Letters (GRL), which, through the magic of multivariate statistics and questionable data weighting, wiped out both the Medieval Warm Period and the subsequent "Little Ice Age" (a cold period from the late 16th century to the mid-19th century), leaving only the 20th-century warming as an anomaly of note.

Messrs. Mann and Wigley also didn't like a paper I published in Climate Research in 2002. It said human activity was warming surface temperatures, and that this was consistent with the mathematical form (but not the size) of projections from computer models. Why? The magnitude of the warming in CRU's own data was not as great as in the models, so therefore the models merely were a bit enthusiastic about the effects of atmospheric carbon dioxide.

Mr. Mann called upon his colleagues to try and put Climate Research out of business. "Perhaps we should encourage our colleagues in the climate research community to no longer submit to, or cite papers in, this journal," he wrote in one of the emails. "We would also need to consider what we tell or request of our more reasonable colleagues who currently sit on the editorial board."

After Messrs. Jones and Mann threatened a boycott of publications and reviews, half the editorial board of Climate Research resigned. People who didn't toe Messrs. Wigley, Mann and Jones's line began to experience increasing difficulty in publishing their results.

This happened to me and to the University of Alabama's Roy Spencer, who also hypothesized that global warming is likely to be modest. Others surely stopped trying, tiring of summary rejections of good work by editors scared of the mob. Sallie Baliunas, for example, has disappeared from the scientific scene.

GRL is a very popular refereed journal. Mr. Wigley was concerned that one of the editors was "in the skeptics camp." He emailed Michael Mann to say that "if we can find documentary evidence of this, we could go through official . . . channels to get him ousted."

Mr. Mann wrote to Mr. Wigley on Nov. 20, 2005 that "It's one thing to lose 'Climate Research.' We can't afford to lose GRL." In this context, "losing" obviously means the publication of anything that they did not approve of on global warming.

Soon the suspect editor, Yale's James Saiers, was gone. Mr. Mann wrote to the CRU's Phil Jones that "the GRL leak may have been plugged up now w/ new editorial leadership there."

It didn't stop there. Ben Santer of Lawrence Livermore National Laboratory complained that the Royal Meteorological Society (RMS) was now requiring authors to provide actual copies of the actual data that was used in published papers. He wrote to Phil Jones on March 19, 2009, that "If the RMS is going to require authors to make ALL data available—raw data PLUS results from all intermediate calculations—I will not submit any further papers to RMS journals."

Messrs. Jones and Santer were Ph.D. students of Mr. Wigley. Mr. Santer is the same fellow who, in an email to Phil Jones on Oct. 9, 2009, wrote that he was "very tempted" to "beat the crap" out of me at a scientific meeting. He was angry that I published "The Dog Ate Global Warming" in National Review, about CRU's claim that it had lost primary warming data.

The result of all this is that our refereed literature has been inestimably damaged, and reputations have been trashed. Mr. Wigley repeatedly tells news reporters not to listen to "skeptics" (or even nonskeptics like me), because they didn't publish enough in the peer-reviewed literature—even as he and his friends sought to make it difficult or impossible to do so.

Ironically, with the release of the Climategate emails, the Climatic Research Unit, Michael Mann, Phil Jones and Tom Wigley have dramatically weakened the case for emissions reductions. The EPA claimed to rely solely upon compendia of the refereed literature such as the IPCC reports, in order to make its finding of endangerment from carbon dioxide. Now that we know that literature was biased by the heavy-handed tactics of the East Anglia mob, the EPA has lost the basis for its finding.

—Mr. Michaels, formerly professor of environmental sciences at the University of Virginia (1980-2007), is a senior fellow at the Cato Institute.